1. Field of the Invention
The present invention relates generally to frozen beverage machines and more particularly to an improved method of controlling the consistency of the beverage produced by a frozen beverage machine.
2. Description of Related Art
Frozen beverage machines are known in the art and have been used for years. These devices produce, for example, a frozen carbonated beverage by freezing a mixture of ingredients typically including syrup, water and carbon dioxide in a freezing chamber. The mixture freezes on the inner surface of the chamber, which is surrounded by a helical coil through which a refrigerant passes. A rotating shaft is disposed inside the chamber which has a plurality of outwardly projecting blades that scrape the mixture off the inside wall of the freezing chamber. Once the carbonated beverage is in the desired frozen state, the product is dispensed from the chamber through a product valve.
A control system controls the refrigeration system to maintain the temperature of the ingredients within the freezing chamber. Small ice crystals that are formed during the initial freezing process will continue to grow to larger crystals. These larger ice crystals present significant quality and operational problems with the frozen beverage machine.
First, since the consistency of a frozen beverage is determined to a large extent by the amount and size of the ice crystals present in the beverage mix, the texture and consistency of the dispensed frozen beverage will over time deteriorate and will thus likely become objectionable to a consumer. Further, the ice crystals can attach and freeze on surfaces inside the freezing chamber causing maintenance and other operational problems, and the ice crystals can stop or reduce the flow of the beverage out of the machine""s dispensing valve. Still further, the instrumentation systems that control the operation of the machine do not function as well due to the larger ice crystals present in the frozen beverage mixture. The beverage then does not flow well so that it can be controlled and produce a consistent drink.
In an attempt to alleviate these and other problems associated with the formation of large ice crystals in the freezing chamber, known frozen beverage machine systems completely defrost the beverage mixture in the freezing chamber. The frozen beverage mixture is returned to a liquid state on a periodic basis (typically every three to six hours), and then the mixture is refrozen. This removes the larger ice crystals. The defrost and refreeze process typically takes from five to 30 minutes or longer. Unfortunately, when the mixing chamber is defrosting, no product can be served to the consumer. This results in lost sales and unhappy customers.
The present invention is directed to improved frozen beverage machine operation methods which overcome, or at least minimizes, problems associated with the prior art.
The present invention provides methods for operating a frozen beverage machine so as to improve the consistency of drinks produced by such machines. It is beneficial to extend the time between defrost cycles, or even to eliminate the complete defrost cycles associated with prior art systems entirely, to keep the frozen beverage machine operable without interruption. The operation of the machine and the quality of the product must not substantially deteriorate during the extended periods of no complete defrost. To improve drink consistency, a novel modification to frozen beverage machine operation is disclosed. Instead of employing a defrost cycle that takes the frozen product completely back to a liquid state, the freezing chamber of the frozen beverage machine is heated for a shorter time period on a more frequent basis. This xe2x80x9cburstxe2x80x9d heating of the freezing chamber can control the size of ice crystals and create advantages to improve the operation of the frozen beverage machine, and in turn, improve the consistency of the beverage produced.
In one aspect of the present invention, the burst heating is conducted on a frequent basis to maintain a consistent frozen drink to reduce the size and amount of ice crystals in the freezing chamber of a frozen beverage machine. The frozen beverage mixture within the freezing chamber approaches a less frozen state, but is not taken to a liquid state as in known defrost cycles, thus maintaining the beverage mixture in a desired consistency.
In an exemplary method of operating a frozen beverage machine in accordance with the invention, the freezing chamber is monitored, and the freezing chamber is heated for a predetermined time period (less than 15 seconds in some embodiments) each time the compressor is to be turned on to refrigerate the freezing chamber. The freezing chamber is then refrigerated until the beverage mixture reaches the desired consistency.